Volatile solvents are used in many industrial processes in which the volatile solvent is used for cleaning purposes. As a result of such use the volatile solvent becomes contaminated with foreign matter. Such contamination may be in a variety of forms. For example, in an auto body shop, it would be in the form of paint residue from spray guns, which are normally cleaned with solvent in a gun washer. In an auto repair shop, the contaminants may well be oil and grease from the cleaning of mechanical parts. Due to the cost of such solvents, environmental concerns, and the cost of disposing of such contaminated volatile solvents, it is desirable to maximize the use that can be made of the solvent by removing the contamination from it by recycling it into the purified solvent form for further use in the industrial process. Various recycling systems exist for use in paint or body shops and as an example, reference is made to our published PCT application no. WO01/03810. In these systems, a batch of contaminated solvent is manually fed into a distiller and processed for use by the operator. When the recovered solvent from the batch is used up, the process is repeated. The contaminant in the form of a sludge is collected in a liner bag which is located in the distillation vessel and the bag is removed at the end of each batch for storage in a separate waste container until such time as the container is removed—typically by a recycling company which will visit the shop periodically and collect the sludge for disposal off-site.
The foregoing has a number of disadvantages. Firstly, the necessity for providing sufficient capacity to accommodate a relatively large quantity of sludge which can accumulate over the period of time between sludge removal operations, coupled with the necessity for providing sufficient recycled solvent from each batch for cleaning operations, translates to the need for a relatively large waste collection container and a relatively large distillation vessel, the combination of which is inefficient in terms of cost and space requirements. Furthermore, since the foregoing process requires that the distiller be run only periodically, this means that a relatively large mass of contaminated solvent must be heated to boiling each time, which is energy intensive, and a relatively large capacity cooling medium is required to condense the solvent vapour from the distillation. Also, operator intervention is inevitably involved to initiate and terminate the batchwise operations. The foregoing disadvantages are particularly pronounced in the case of small operations such as auto repair and paint shops.